The rapid increase of the penetration of renewable energy resources in power systems brings great difficulties to the power system operator in solving the security-constrained unit commitment (SCUC). This paper proposes a SCUC model considering the impact of uncertainties of environmental factors on the transmission power limits by the dynamic capacity-increase technique. The heat distribution process, including thermal radiation, thermal convection, and solar absorption, is regarded as the decisive factor of the steady-state temperature of the transmission line conductor. Along with uncertainties of other factors like wind speed and sunshine intensity, this paper applies multi-scenario technology to transform the uncertain problem into multiple deterministic scenario problems. Finally, the proposed model is verified on the IEEE 24-bus test system. Finally, the effectiveness and efficiency of the proposed model are demonstrated on several test systems.